Reports of the rare occurrence of Guillain-Barré syndrome (GBS) or chronic inflammatory demyelinating polyradiculoneuropathy
(CIDP) following immunisation1 and recurrence of symptoms following subsequent immunisation2 have given rise to concern over the safety of vaccine administration in this patient group. Similar concerns have been addressed
and dismissed in patients with multiple sclerosis,3 but no such information exists for inflammatory neuropathy. To provide more information about vaccine safety in GBS and CIDP
we audited the recurrence of neurological symptoms following immunisation.

The Guillain-Barré Syndrome Support Group, a British patient organisation, posted 3000 questionnaires to its members, asking
them to identify their illness, record all immunisations administered after their illness, and describe any symptoms within
six weeks of immunisation suggestive of recurrence of GBS or worsening of CIDP.

All but one of the patients who reported neurological symptoms after immunisation were contacted by telephone to confirm their
history and to grade their symptoms using the modified Rankin scale.4 For the patient who could not be contacted by telephone, the patient's consultant neurologist provided the information. Questionnaires
were sent to the general practitioner for each patient who reported a “relapse” to confirm which vaccine had been administered.

A total of 1114 patients (37.1%) completed the questionnaires, of whom 927 had had GBS, 179 had CIDP, and eight were excluded
because they had other diseases. Of the 927 patients with GBS, 311 had received immunisations since having GBS. Eleven (3.5%,
95% confidence limits (CL) 1.8%, 6.2%) reported symptoms including increased fatigue, weakness, numbness, and paraesthesiae,
but these were usually mild and no patient required hospitalisation or treatment. In three cases symptoms came on within 24
hours of immunisation and all but one developed symptoms within one week of immunisation. One patient reported symptoms rendering
him unable to walk unaided or drive for six weeks, which increased his modified Rankin scale score from grade 2 to 4.

Influenza, tetanus, and typhoid were the most common immunisations associated with a relapse after GBS but the number of patients
who reported symptoms was small compared with the total numbers receiving each of these vaccines (table 1). Although the results
suggest that some vaccines that are administered less frequently (such as diphtheria) may be associated with a higher relapse
risk, the numbers were small and most of these vaccines were administered at the same time as other vaccines.

Of the 311 patients with GBS who had received vaccines after having GBS, 29 had also received a vaccine in the six weeks before
the onset of their initial illness. Two of these patients (6.9%, 95% CL 0.85%, 22.8%) had a recurrence of symptoms after a
second, different, vaccine was subsequently administered.

Of the 179 patients with CIDP, 65 had been immunised after disease onset. Five reported worsening of neurological symptoms
following immunisation. In three the symptoms were similar to a typical relapse of their CIDP, but only one of these patients
required treatment within two months of immunisation. The other two patients with CIDP were immunised when already experiencing
mild neurological symptoms, which then worsened, so that their modified Rankin scale score increased from 1 to 4 and they
became dependent on a walking stick and unable to drive.

Of the patients with CIDP who experienced a relapse after immunisation, two relapses occurred among 23 patients who received
the tetanus vaccine, giving a risk of relapse of 8.7%. Two of 46 (4.3%) patients with CIDP had relapses after influenza vaccine,
of whom one had simultaneous pneumococcus vaccine. Two of six (33%) patients, including the last mentioned, experienced relapses
after pneumococcus vaccine. Fourteen patients with CIDP had no symptoms of relapse following immunisation with typhoid vaccine.
Between one and seven patients with CIDP had no symptoms after yellow fever, diphtheria, meningococcus, oral polio, BCG, hepatitis
A, hepatitis B, cholera, or rubella vaccine.

This audit of patients with GBS and CIDP who have received vaccines suggests that the risk of relapse following immunisation
is low. The response rate to the questionnaire was small as a proportion of the membership of the GBS Support Group. This
is partly because an unknown but large proportion of members are relatives or friends and not former GBS or CIDP patients.

Only 11 of 311 patients with GBS (3.5%, 95% CL 1.8%, 6.2%) who had been immunised after having the disease reported a recurrence
of symptoms. All of the vaccines that were associated with neurological symptom recurrence had also been received by many
more patients who remained well. Some of the patients who reported symptoms after receiving vaccines had also received the
same or other vaccines on other occasions without experiencing any problems. Only one respondent experienced symptoms that
increased their modified Rankin scale score. The risk of relapse severe enough to alter the modified Rankin scale score is
0.3% (95% CL 0.01%, 1.78%) while the risk of a relapse requiring treatment or hospitalisation is at most 1.18% (95% CL).

It is more difficult to draw conclusions about the risk of immunisation for relapse in CIDP because our sample size was smaller.
Five (7.7%, 95% CL 2.5%, 17.0%) of 65 patients noted a return of symptoms following immunisation. The reports of minor symptoms
or acceleration of deterioration following influenza and pneumococcus vaccines merit caution in recommending these immunisations
in patients with CIDP, although the risk of infection in immunosuppressed patients may outweigh any potential risk. Of greatest
concern is the risk of relapse following tetanus toxoid, which was 8.7% (95% CL 1.7%, 28.0%) in our patient sample. In view
of these figures and previous reports of relapse of CIDP following tetanus toxoid2,5 patients may wish to avoid routine tetanus toxoid immunisation.

Finally, it is important to acknowledge the difficulties in drawing conclusions from a questionnaire in which the patients
reported their diagnostic classification and relapses. It is intuitively likely that more patients who experienced symptoms
following immunisation responded to the questionnaire, which would overestimate the frequency of relapses. Consequently the
true risks of relapse following immunisations after GBS or in CIDP may be less than those discovered in this audit.